GPS System on people?

[DCJ311]

I have actually read about this idea, mostly to put on children as a deterrent to kidnapping. Basically you use a microchip or an ankle bracelet that's monitored to know where the person is at all times. I don't know if it's actually out yet, but it seems like a great idea to own, even though the odds of getting kidnapped are pretty low. There's probably other advantages to it, like if you're walking around in a big city, you could use a hand-held device to figure out how to get from point A to point B much more easily based on where you are.

So, if such a device were available, how many people would use it on themselves or their kids if relatively inexpensive?